Helicity resonant influence on the local Alfvén resonance structure in straight stellarators

Distribution of antenna-driven electromagnetic wave fields within the local Alfven resonance is studied under resonant conditions such that the axial period of the fundamental harmonic of the magnetohydrodynamic oscillations in the axial direction is twice as large as the pitch length, and the poloidal number of the fundamental harmonic is twice as small as the polarity of the helical coils. It is shown that taking account of the helical inhomogeneity of the steady magnetic field can remove the infinite discontinuity of the wave fields that takes place in a straight magnetic field rather than with electron inertia or a finite ion Larmor radius.